The invention is directed to a hydraulically controlled disconnect system for a friction clutch of vehicles with a manually shiftable transmission, whereby the disconnect system has slave cylinder with a pressure housing which is arranged concentrically on a gear box input shaft which connects an internal combustion engine with the gear shift drive, whereby a guide sleeve is arranged at a radial distance from the pressure housing to form a circularly shaped pressure chamber, and a ring piston is movably guided axially in the pressure chamber, which is provided with a seal on its pressure chamber side, the sealing lips of which are arranged radially spread apart.
Disconnect systems of the above-mentioned type of construction are generally known and find application in motor vehicles. A representative disconnect system is known from DE-C 31 48 183 in which a ring piston axially delimits a pressure chamber. A sealing ring is allocated on the pressure chamber side of the ring piston, the sealing lips of which lie radially spread apart sealing on the components between which the ring piston is guided. The rigid sealing arrangement on the ring piston provided in this known disconnection system has the disadvantage that, for example, axial vibrations, which are triggered by the crankshaft of the internal combustion engine, are transmitted through the friction clutch and the clutch disconnect bearing to the ring piston, and from there undamped into the hydraulic system. These pressure oscillations can initiate a disadvantageous "crawling" on the clutch pedal which reduces comfort.
A further ring piston seal is known from U.S. Pat. No. 4,821,627 in which a radial extension on one side of the ring piston is sprayed on nearly all sides by sealing material. Even this solution makes no vibration compensation possible so that the vibrations are likewise transmitted undamped to the clutch pedal as before.
Furthermore, clutch disconnecting systems are known in connection with which the seal has no connection on the ring piston. The seal is moreover held in a separate seal carrier which is axially introduced to the ring piston. This solution is very much subject to disturbance and requires, for example, a secondary suction-sensitive valve for a vacuum filling of the disconnecting system.